The ISIL clashed with Kurdish forces in the town of Makhmur near Arbil, the capital of the Kurdish semi-autonomous zone.

World Bulletin/News Desk

ISIL militants extended their gains in northern Iraq on Thursday, seizing three more towns and gaining a foothold near the Kurdish region, witnesses said.

The advance came after the Sunni militants inflicted a humiliating defeat on Kurdish forces in a weekend sweep in the north.

The ISIL clashed with Kurdish forces on Wednesday in the town of Makhmur near Arbil, the capital of the Kurdish semi-autonomous zone.

In the latest advance, its fighters seized Makhmur and the mainly Christian town of Tilkaif, as well as Al Kwair, witnesses said.

Militants also have seized one of the last remaining government bases in the northern province of Raqqa, activists said on Thursday, in clashes a monitoring group said killed more than 40 people.

Last month the group killed at least 50 Syrian government forces as they took over parts of another base in the area.

On Thursday, a monitoring group and Islamic State supporters said the militants had taken full control of the 93th Brigade military base after an attack that opened with multiple suicide car bomb attacks.

"Allahu Akbar (God is greatest), we announce ... the total liberation of the 93th Brigade," said a Twitter feed which regularly publishes news from Islamic State in Raqqa province.

The Britain-based Syrian Observatory for Human Rights said at least 27 pro-government fighters were killed after three fighters blew themselves up in car bombs at the gates and around the base and in the ensuing clashes.

At least 11 ISIL fighters were killed, added the group, which monitors violence in Syria through a network of sources. It said "dozens" more were wounded.

The Observatory estimates that the Islamic State controls about 35 percent of Syrian territory - although much of that is desert.

The government has meanwhile consolidated its grip on the country's more densely populated central areas, including a corridor stretching from the capital Damascus to the Mediterranean coast in the west.

More than 170,000 people have been killed in Syria's civil war, which pits overwhelmingly Sunni Muslim rebels against President Bashar al-Assad, a member of the Shi'ite-derived Alawite minority, backed by Shi'ite militias from Iraq and Lebanon.